Drag recovery scheme using boundary layer ingestion

ABSTRACT

Technologies are described herein for a drag recovery scheme using a boundary layer bypass duct system. In some examples, boundary layer air is routed around the intake of one or more of the engines and reintroduced aft of the engine fan in the nozzle duct in a mixer-ejector scheme. Mixer-ejectors mix the boundary layer flow to increase mass flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.Non-Provisional patent application Ser. No. 17/501,492 filed on Oct. 14,2021 and entitled “DRAG RECOVERY SCHEME USING BOUNDARY LAYER INGESTION,”the entirety of which is incorporated herein by reference. The U.S.non-provisional patent application claims priority to InternationalApplication No. PCT/US2020/041018 filed on Jul. 7, 2020 and entitled“DRAG RECOVERY SCHEME USING BOUNDARY LAYER INGESTION,” the entirety ofwhich is incorporated herein by reference. The international applicationclaims the benefit of priority of U.S. Provisional Patent ApplicationSer. No. 62/871,469, filed on Jul. 8, 2019, which is incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of aircraftpropulsion. In particular, the present invention is directed to dragrecovery scheme using boundary layer ingestion.

BACKGROUND

Blended wing body aircraft have great potential for increasingefficiency of air travel, as a result of the shape of the blended wingbody. However, in some cases, positioning of engines on blended wingbody aircraft may require large heavy pillars to place the engine faraway from the blended wing body and prevent the engine from receivingboundary layer air.

SUMMARY OF THE DISCLOSURE

Technologies are described herein for a drag recovery scheme using aboundary layer bypass duct system. In some examples, boundary layer airis routed around the intake of one or more of the engines andreintroduced aft of the engine fan in the nozzle duct in a mixer ejectorscheme. Mixer-ejectors mix the boundary layer flow to increase massflow.

In an aspect, an aircraft includes a blended wing body, at least oneengine housed within a nacelle, wherein the at least one engine ismechanically coupled to at least one fan, at least one bypass intakeduct configured to receive boundary layer air from a top surface of theblended wing body, the at least one bypass intake duct located proximateto a fan intake of the at least one fan, at least one bypass exhaustduct located proximate to a fan exhaust of the at least one fan, whereinthe at least one bypass exhaust duct is configured to output theboundary layer air into the fan exhaust of the at least one fan, apassageway, located substantially between the blended wing body and theat least one engine, fluidically connecting the at least one bypassintake duct with the at least one bypass exhaust duct and configured todirect the boundary layer air from the at least one bypass intake ductto the at least one bypass exhaust duct, and a nozzle configured todirect the boundary layer air and the fan exhaust out of a nozzle exitlocated forward of a trailing end of the blended wing body

Another aspect relates to, a method of reducing drag of an aircraft,including a blended wing body and at least one engine housed within anacelle, wherein the at least one engine is mechanically coupled to atleast one fan. The method may include receiving, by at least one bypassintake duct, boundary layer air from a top surface of the blended wingbody, the at least one bypass intake duct located proximate to a fanintake of the at least one fan, fluidically connecting, by a passagewaylocated substantially between the blended wing body and the at least oneengine, the at least one bypass intake duct with at least one bypassexhaust duct located proximate to a fan exhaust of the at least one fan,directing, by the passageway, the boundary layer air from the at leastone bypass intake duct to the at least one bypass exhaust duct,outputting, using the at least one bypass exhaust duct, the boundarylayer air into the fan exhaust of the at least one fan, and directing,using a nozzle, the boundary layer air and the fan exhaust out of anozzle exit located forward of a trailing edge of the blended wing body.

These and other aspects and features of non-limiting embodiments of thepresent invention will become apparent to those skilled in the art uponreview of the following description of specific non-limiting embodimentsof the invention in conjunction with the accompanying drawings.

This Summary is provided to introduce a selection of technologies in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intendedthat this Summary be used to limit the scope of the claimed subjectmatter. Furthermore, the claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in any part ofthis disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a side-view illustration of a blended wing body (“BWB”)aircraft using a boundary layer bypass duct system, according to variousexamples described herein;

FIG. 2 is a side-view illustration of a boundary layer bypass ductsystem, according to various examples described herein;

FIG. 3 is a side-view illustration of a boundary layer bypass ductsystem using multiple ducts, according to various examples describedherein;

FIG. 4 is a side-view illustration of a boundary layer bypass ductsystem using an extended nacelle, according to various examplesdescribed herein; and

FIG. 5 is a front-view illustration of an extended inlet for a boundarylayer bypass duct system, according to various examples describedherein.

The drawings are not necessarily to scale and may be illustrated byphantom lines, diagrammatic representations and fragmentary views. Incertain instances, details that are not necessary for an understandingof the embodiments or that render other details difficult to perceivemay have been omitted.

DETAILED DESCRIPTION

Conventional aircraft typically consist of a so-called “tube and wing”configuration, or, a blended-wing body (“BWB”) configuration, wherethere is no clear delineation between the wings and the main body of theaircraft. When in flight, various layers of air flow form along thelength of the fuselage. Closer to the fuselage, a boundary layerdevelops. The boundary layer is the part of the flow near the surface ofthe fuselage where friction slows down the local flow. Directly at thewall of the body, flow speed is zero and increases as the distance fromthe surface of the fuselage increases.

Boundary layer ingestion (“BLI”) has been studied as a means to reduceoverall airplane energy consumption by accelerating the slow wake tomake thrust versus accelerating freestream flow at full flight velocity.Thrust is generated by a given accelerated a given mass flow by a givendifference in velocity (“Δv”). The energy consumed varies with the givenmass flow and the Δv squared. By incorporating slower inflow to theengine an energy improvement is realized.

Today, studies of jet engine BLI have been confined to BLI at the faceof the engine exposing the fan to turbulent flow with a large speeddifference with the rest of the inflow. This may make it difficult todesign a fan blade that can tolerate the large inflow angle changes andtolerate the high loads and vibration it causes. Further, as theaircraft increases airspeed, the various turbulent flows and theboundary layer become increasing complex to design for, resulting in afan blade design that may be very efficient at one airspeed butinefficient at other airspeeds, or a fan blade with mediocre efficiencyover a wide range of airspeeds.

It is with respect to these and other considerations that the disclosuremade herein is presented.

The following detailed description is directed to technologies for adrag recovery scheme using boundary layer bypass duct system. As notedabove, in some examples, a BWB aircraft can include one or more nacellesthat house a jet engine. In some examples, the nacelles abut (or areinstalled onto) a top surface of the aircraft. In other examples, thenacelles are partially within the aircraft and partially outside of theaircraft (“partially hidden”). Partially hidden means that that thenacelles are partially below the surface of the aircraft.

When the BWB aircraft is moving through the air at some velocity throughthe use of the one or more jet engines (“main engines”), a boundarylayer of air forms on the aircraft. All other factors being equal, theboundary layer forms along the entire length of the aircraft. Theboundary layer represents slow or stagnant air along the surface of theaircraft, and thus, represents a force of drag while the aircraft is inmotion.

In various types of aircraft in which the intake of the engine is inline with the movement of some layers of the boundary layer, such as asemi-buried nacelle, the engine design may be used to try to use some ofthat boundary layer air. As noted above, in some examples, someconventional engines use modified fan blades that are designed to pullin at least a portion of the boundary layer air and use the air in theengine. A problem with this approach is that, due to the changingturbulent nature of the boundary layer air at difference speeds, the fanblades can be designed either for optimal efficiency at a singleaircraft speed or a moderate efficiency over a range of aircraft speeds.While providing some increased efficiency at certain airspeeds, the useof the boundary layer air in the intake can actually reduce theefficiency of the engine at speeds for which the fan blades were notdesigned to be optimal.

In examples of the presently disclosed subject matter, instead ofintroducing boundary air into the intake of the engine, the engine isdesigned with a bypass duct system that pulls the boundary air aroundthe engine, reintroducing the boundary air aft of the engine fan in thenozzle duct in a mixer-ejector scheme. Mixer-ejectors mix the bypassedexternal flow in a duct to increase mass flow and reduce the delta-V tomake approximately equivalent thrust.

The slow-moving air introduced into the wake of the airframe can be anideal source, even at high airplane flight speeds. The airframeboundary-layer (wake) is ducted to the inside of the fan nozzle behindthe fan where it will preferably cause little no vibration or noisepenalty. The slot that introduces this flow can be optimally severalslot heights upstream of the nozzle exit to achieve full effect. In someexamples, the boundary layer on the top surface of the aircraft and thebottom surface of the aircraft can be introduced into the bypass duct,increasing the benefit.

While the presently disclosed subject matter may be described withrespect to what is termed as examples, embodiments, and the like, it isunderstood that the presently disclosed system is not limited to thedisclosed embodiments.

FIG. 1 is a side-view illustration of a blended wing body (“BWB”)aircraft 100, according to various examples described herein. The BWBaircraft includes a fuselage 102. The fuselage includes a port wing 104Aand a starboard wing 104B. To propel the aircraft 100, the aircraftincludes main engine 106A housed within nacelle 108A and main engine106B housed within nacelle 108B. The main engines 106A and/or 106B maybe various types of engines, including, but not limited to, turbojet,turboprop, turbofan, and turboshaft. As used herein, “nacelle” 108A and108B is a housing, separate from fuselage 102, that holds a flightcomponent, such as main engines 106A and 106B, respectively. It shouldbe noted that although the presently disclosed subject matter isdescribed in terms of a two-engine BWB aircraft, aircraft 100, examplesof the presently disclosed subject matter may be used with other numbersof main engines, or other equipment, and are considered to be within thescope of the presently disclosed subject matter.

The aircraft 100 further includes intake ducts 110A and 110B. The intakeducts 110A and 110B receive boundary air 112A and 112B, move theboundary air 112A and 112B around the main engines 106A and 106B andnacelles 108A and 108B, respectively, and reintroduces the boundary air112A into an exhaust flow 114A of main engine 106A and an exhaust flow114B of the main engine 106B. The movement of the boundary air 112A and112B may be accomplished using a duct internal, external, or partiallyinternal and partially external to the nacelles 108A and 108B. It shouldbe noted that the presently disclosed subject matter does not requirethat the boundary air 112A or 112B comprise all boundary air flow thatmay exist, as some boundary air may still flow through a main engineintake.

FIG. 2 is a side-view illustration of the aircraft 100. In FIG. 2, thefuselage 102 is illustrated with the main engine 106A and nacelle 108A.As illustrated, a part of the nacelle 108A of the main engine 106A ispartially below a surface plane AB of the fuselage 102, sometimesreferred to as a “partially-buried” or “semi-buried” nacelle. It shouldbe understood that this is merely an example, as the presently disclosedsubject matter may be used with fully or non-buried nacelles/engines.

Illustrated in FIG. 2 are three airflows. Proximal airflow 212 generallyrepresents the boundary layer air that forms on and proximate to theouter layer of the fuselage 102. Distal airflow 214 generally representsfree air that flows outside of the proximal airflow 212. Theintermediate airflow 216 generally represents an interface between theproximal airflow 212 and the distal airflow 214. It should be noted thatthe airflows 212, 214, and 216 are not drawn to any particular scale.Further, it should be noted that the air represented by the airflows212, 214, and 216 do not have exact or clearly definable layers.

As illustrated, the proximal airflow 212 (generally representing theboundary layer air) is introduced into the intake duct 110A, movedthrough passageway 222A, and is exhausted through an exhaust duct 224A,shown in more detail below. Although not beholden to one scientificprinciple, it is understood that turbulent entrainment of the proximalairflow 212 essentially “pulls” the airflow 212 into the passageway 222Aand the exhaust duct 224A. In the exhaust 226A of the main engine 106A,the faster flow of the exhaust 226A is slowed, and the slower flow ofthe proximal airflow 212 is sped up in a “turbulent mixing” cone. Theincreasing of the velocity of the proximal airflow 212 creates a vacuum,pulling airflow 212 into the passageway 222A. The reduction in pressurein the passageway 222A (causing the pulling of the proximal airflow 212into the passageway 222A) can be felt at the intake duct 110A, reducingthe pressure buildup of stagnant boundary layer air, increasing thrust.

In a different manner than can be found in conventional aircraft, thebeneficial effects of the partial vacuum in the passageway 222Agenerally increases as the speed of the aircraft 100 increases due toincreased main engine 106A thrust. With higher main engine 106A thrust,the velocity of the exhaust 226A increases. Because the velocity of theproximal airflow 212 is essentially constant, as the velocity of theexhaust 226A increases, the differential pressure created in the“turbulent mixing” cone in the exhaust 226A increases, thus increasingthe amount of the proximal airflow 212 pulled into the exhaust 226A andthe accompanying benefits. At some general location downstream of theaircraft 100, the proximal airflow 212 and the exhaust 226A arecompletely mixed, with constant pressure and turbulent flow. Other typesof mechanisms may be used to introduce the proximal airflow 212, suchas, but not limited to, venturi valves and the like.

FIG. 3 is a close-up, side-view illustration of a bypass duct system. InFIG. 3, the fuselage 302 of the aircraft 300 includes a main engine 306Ahoused within a nacelle 308A. The configuration illustrated in FIG. 3 isa semi- or partial-buried nacelle configuration. The fuselage 302further includes an intake duct 310A located proximate to the intakeside of the main engine 306A, a passageway 322A, and an exhaust duct324A, which opens to the exhaust 326A of the main engine 306A. Theintake duct 310A is located proximate to an intake 328A of the mainengine 306A. The passageway 322A fluidically connects the intake duct 310A with the exhaust duct 324A to provide for an air passage from theintake duct 310A to the exhaust duct 324A.

The intake duct 310A is located proximate to the nacelle 308A and inline with or in the boundary layer air 330A proximate to the intake328A. The boundary layer air 330A is introduced through the intake ducts310A, moved through the passageway 322A, and is exhausted into theexhaust 326A through the exhaust duct 324A. The exhausted boundary layerair 332A mixes with the exhaust 326A in mixing region 334A. In someexamples, the exhausted boundary layer air 332 is introduced into theexhaust 326A within the nacelle 308A.

FIG. 4 is a close-up, side-view illustration of a dual bypass ductsystem. In FIG. 4, the fuselage 402 of the aircraft 400 includes a mainengine 406A housed within a nacelle 408A. The configuration illustratedin FIG. 4 is a semi- or partial-buried nacelle configuration. Thefuselage 402 further includes an upper intake duct 410A, a passageway422A, and an exhaust duct 424A, which opens to the exhaust 426A of themain engine 406A.

The upper intake duct 410A is located proximate to an intake 428A of themain engine 406A. The upper intake duct 4 10A is further locatedproximate to the nacelle 408A and in line with or in an upper boundarylayer air 430A proximate to the intake 428A. The upper boundary layerair 430A is introduced through the upper intake duct 4 10A, movedthrough the passageway 422A, and is exhausted into the exhaust 426Athrough the exhaust duct 424A. The exhausted upper boundary layer air432A mixes with the exhaust 426A in mixing region 434A. In someexamples, the exhausted boundary layer air 432A is introduced into theexhaust 426A within the nacelle 408A.

The fuselage 402 further includes a secondary intake duct 436A. Thesecondary intake duct 436A receives secondary boundary layer air 438Blocated proximate to a second layer of the fuselage 402. In the exampleillustrated in FIG. 4, the secondary intake duct 436A is locatedproximate to the lower surface of the fuselage 402. The secondaryboundary layer air 438A is introduced through the secondary intake duct436A, moved through a passageway 440A, and is exhausted into the exhaust426A through the exhaust duct 424A. The exhausted secondary boundarylayer air 442A mixes with the exhaust 426A in mixing region 434A. Insome examples, the exhausted secondary boundary layer air 442A isintroduced into the exhaust 426A within the nacelle 408A.

FIG. 5 is a close-up, side-view illustration of a bypass duct systemwith an extended bypass intake. In FIG. 5, the fuselage 502 of theaircraft 500 includes a main engine 506A housed within a nacelle 508A.The configuration illustrated in FIG. 5 is a semi- or partial-buriednacelle configuration. The fuselage 502 further includes an upper intakeduct 510A, a passageway 522A, and an exhaust duct 524A.

In FIG. 5, the upper intake duct 510A is located a distance XY from anintake 528A of the main engine 506A using an intake extender 530A. Theintake extender 530A increases the distance from the intake 528A of themain engine 506A and the intake of the upper intake duct 510A. Locatingthe upper intake duct 510A from the intake 528A of the main engine 506Acan provide various benefits. For example, the partial vacuum created bythe mixing in the exhaust of the engine (described above) can be feltfurther closer to the bow (or front) of the aircraft 500, potentiallyreducing the drag effect of the boundary air.

Based on the foregoing, it should be appreciated that technologies for adrag recovery scheme using boundary layer bypass duct system have beendisclosed herein. It is to be understood that the invention defined inthe appended claims is not necessarily limited to the specific featuresor acts described herein. Rather, the specific features or acts aredisclosed as example forms of implementing the claims.

The subject matter described above is provided by way of illustrationonly and should not be construed as limiting. Various modifications andchanges can be made to the subject matter described herein withoutfollowing the example configurations and applications illustrated anddescribed, and without departing from the true spirit and scope of thepresent invention, aspects of which are set forth in the followingclaims.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments, what has been described herein is merelyillustrative of the application of the principles of the presentinvention. Additionally, although particular methods herein may beillustrated and/or described as being performed in a specific order, theordering is highly variable within ordinary skill to achieve methods,systems, and software according to the present disclosure. Accordingly,this description is meant to be taken only by way of example, and not tootherwise limit the scope of this invention.

Exemplary embodiments have been disclosed above and illustrated in theaccompanying drawings. It will be understood by those skilled in the artthat various changes, omissions and additions may be made to that whichis specifically disclosed herein without departing from the spirit andscope of the present invention.

What is claimed is:
 1. An aircraft, comprising: a blended wing body; atleast one engine housed within a nacelle, wherein the at least oneengine is mechanically coupled to at least one fan; at least one bypassintake duct configured to receive boundary layer air from a top surfaceof the blended wing body, the at least one bypass intake duct locatedproximate to a fan intake of the at least one fan; at least one bypassexhaust duct located proximate to a fan exhaust of the at least one fan,wherein the at least one bypass exhaust duct is configured to output theboundary layer air into the fan exhaust of the at least one fan; apassageway, located substantially between the blended wing body and theat least one engine, fluidically connecting the at least one bypassintake duct with the at least one bypass exhaust duct and configured todirect the boundary layer air from the at least one bypass intake ductto the at least one bypass exhaust duct; and a nozzle configured todirect the boundary layer air and the fan exhaust out of a nozzle exitlocated forward of a trailing end of the blended wing body
 2. Theaircraft of claim 1, wherein the at least one bypass exhaust duct isconfigured to mix the boundary layer air and the fan exhaust of the atleast one fan.
 3. The aircraft of claim 2, wherein the at least onebypass exhaust duct has a duct height, the at least one bypass exhaustduct is located forward a nozzle exit by at least a distance within anozzle, and the distance is no less than the duct height.
 4. Theaircraft of claim 2, wherein the at least one bypass exhaust duct isconfigured to mix the boundary layer air and the fan exhaust of the atleast one fan using a turbulent mixing cone.
 5. The aircraft of claim 2,wherein the boundary layer air exits the at least one bypass exhaustduct between the blended wing body and the at least one engine into amixing region in which the fan exhaust of the at least one fan is mixedwith the boundary layer air.
 6. The aircraft of claim 3, wherein themixing region is within the nacelle.
 7. The aircraft of claim 1, whereinthe nacelle is semi-buried.
 8. The aircraft of claim 1, furthercomprising: a second bypass intake duct configured to receive secondboundary layer air from a bottom surface of the blended wing body; asecond bypass exhaust duct located proximate to the fan exhaust of theat least one fan; and a second passageway fluidically connecting thesecond bypass intake duct with the second bypass exhaust duct andconfigured to direct the second boundary layer air from the secondbypass intake duct to the second bypass exhaust duct.
 9. The aircraft ofclaim 1, further comprising: a second fan housed within a secondnacelle; a second bypass intake duct configured to receive a secondboundary layer air from the top surface of the blended wing body, thesecond bypass intake duct located proximate to a second fan intake ofthe second fan; a second bypass exhaust duct located proximate to asecond fan exhaust of the second fan; and a second passagewayfluidically connecting the second bypass intake duct with the secondbypass exhaust duct and configured to direct the second boundary layerair from the second bypass intake duct to the second bypass exhaustduct.
 10. The aircraft of claim 1, further comprising a bypass intakeextender configured to increase a distance from the fan intake of the atleast one fan and the at least one bypass intake duct.
 11. A method ofreducing drag of an aircraft, comprising a blended wing body, and atleast one engine housed within a nacelle, wherein the at least oneengine is mechanically coupled to at least one fan and the methodcomprises: receiving, by at least one bypass intake duct, boundary layerair from a top surface of the blended wing body, the at least one bypassintake duct located proximate to a fan intake of the at least one fan;fluidically connecting, by a passageway located substantially betweenthe blended wing body and the at least one engine, the at least onebypass intake duct with at least one bypass exhaust duct locatedproximate to a fan exhaust of the at least one fan; directing, by thepassageway, the boundary layer air from the at least one bypass intakeduct to the at least one bypass exhaust duct; outputting, using the atleast one bypass exhaust duct, the boundary layer air into the fanexhaust of the at least one fan; and directing, using a nozzle, theboundary layer air and the fan exhaust out of a nozzle exit locatedforward of a trailing edge of the blended wing body.
 12. The method ofclaim 11, further comprising mixing, using the at least one bypassexhaust duct, the boundary layer air and the fan exhaust of the at leastone fan.
 13. The method of claim 12, wherein the at least one bypassexhaust duct has a duct height, the at least one bypass exhaust duct islocated forward of a nozzle exit by at least a distance within a nozzle,and the distance is not less than the duct height.
 14. The method ofclaim 12, further comprising, mixing, by the at least one bypass exhaustduct, the boundary layer air and the fan exhaust of the at least one fanusing a turbulent mixing cone.
 15. The method of claim 12, wherein theboundary layer air exits the at least one bypass exhaust duct betweenthe blended wing body and the at least one engine into a mixing regionin which the fan exhaust of the at least one fan is mixed with theboundary layer air.
 16. The method of claim 13, wherein the mixingregion is within the nacelle.
 17. The method of claim 11, wherein thenacelle is semi-buried.
 18. The method of claim 11, further comprising:receiving, by a second bypass intake duct, second boundary layer airfrom a bottom surface of the blended wing body; fluidically connecting,by a second passageway, the second bypass intake duct with a secondbypass exhaust duct located proximate to the fan exhaust of the at leastone fan; and directing, by the second passageway, the second boundarylayer air from the second bypass intake duct to the second bypassexhaust duct.
 19. The method of claim 11, wherein the aircraft furthercomprises a second fan housed within a second nacelle, and the methodfurther comprises: receiving, by a second bypass intake duct, a secondboundary layer air from the top surface of the blended wing body, thesecond bypass intake duct located proximate to a second fan intake ofthe second fan; fluidically connecting, by a second passageway, thesecond bypass intake duct with a second bypass exhaust duct locatedproximate to a second fan exhaust of the second fan; and directing, bythe second passageway, the second boundary layer air from the secondbypass intake duct to the second bypass exhaust duct.
 20. The method ofclaim 11, further comprising increasing, by a bypass intake extender, adistance from the fan intake of the at least one fan and the at leastone bypass intake duct.